生态需水在输水工程生态影响评价中的应用

以南水北调工程为例的输水管道工程在解决我国水资源供需矛盾和地域分配不均的问题中发挥着重要作用,输水管道工程的建设在产生巨大社会、经济、生态效益的同时,也给工程建设区域、调水相关区域脆弱的生态环境带来新的问题。工程建设的环境影响评价往往关心工程建设、运行时期对相关区域内主要环境要素的影响、响应及评价,而对工程建设相关的关键生态系统的影响关注较小。而南水北调等输水管道工程是与水密切相关的国家级大型工程,对工程建设区域、影响区域的水生生态系统产生较大的影响,如何科学、定量地评价输水工程对关键生态系统的影响是输水工程建设管理人员关注的热点之一。基于对生态需水评价理论与方法的总结及输水工程生态影响定量评价难点的分析,对生态需水与水生生态系统健康之间相辅相成的关系进行研究,提出了将生态需水引入输水工程生态影响评价的技术路径与评价模型。以南水北调中线工程为例,对其影响范围内的生态需水量进行评价,进而判断工程建设运行对相关区域关键生态系统的影响。

The application of ecological water requirements in the ecological impact assessment of a water conveyance project

The water conveyance pipeline project plays an important role in solving the supply and demand contradictions and uneven geographic distribution of water in China. Considering the water conveyance pipeline project from a socially beneficial perspective, water supply would increase after the project completion in northern China, where there is heavy water scarcity; water environmental carrying capacity in these regions would be enhanced as well. From an economically beneficial perspective, construction of the pipeline for the water conveyance project would help to increase the regional output values of industry and agriculture, as well as create more jobs for the local residents and others. From an eco-environmentally beneficial perspective, the water conveyance pipeline would provide new solutions to problems such as groundwater overdraft and water pollution in the water-recipient regions. However, even with the aforementioned social, economic, and eco-environmental benefits to relevant regions, the construction of the water conveyance project also creates new problems for the fragile ecosystem and environment such as disruption of the ecosystem balance in the water source area, damage of the phreatic aquifer along the pipeline project, and so on. Therefore, we need to invest more funds, technology, and personnel into the construction and management of the water conveyance project because of this duality. At the same time, there are many obstacles to an ecological impact assessment of water conveyance projects, one of the most important being the lack of quantitative assessment methods. The determination of assessment scope, lack of ecological monitoring and feedback activities are also significant issues to consider in ecological impact assessments. How to assess the eco-environmental impact of water conveyance projects scientifically and quantitatively is a key decision to project construction and management. Initially, when the concepts of ecological water requirements were proposed in 1998, many researchers from various limnological disciplines of study, such as rivers, lakes, and wetlands, paid close attention to these concepts and relevant methods. Researchers interpreted and analyzed the concepts of ecological water requirements from hydrology, hydraulics, and ecosystem perspectives. The assessment methods and calculation models of ecological water requirement were enriched gradually, and the typical methods, such as Tennant, R2CROSS, and IFIM, among others, were widely applied in the assessment of ecological water requirement of rivers, lakes, and wetlands. In this study, based on the assessment theory, methods of ecological water requirement, and the quantitative analysis of ecological impact assessment, further reinforcing the relationship between ecological water requirement and ecosystem health, we established a technological roadmap and an estimation model for the eco-environmental impacts of the water conveyance project, which lie within the ecological water requirements. Using the Middle Route of the South-to-North Water Division Project as a case study, we assess the ecological water requirements of the relevant influenced regions. The results show that water transfer during the first phase of the South-to-North Water Division Project would not have a serious impact on water resources and the ecosystem in the region and would not result in the obvious ecosystem degradation. Additionally, the results prove that methods of ecological water requirement assessment are helpful to ecological impacts assessment.